Influence of point defects in KTaO3 on low-temperature dielectric relaxation

Polar fluctuations in Mn substituted KTaO3 ceramics

“…14 In addition, the thermal polar fluctuations in KTaO 3 :Mn will result in a significant stiffening of the soft phonon mode. This has been discussed in earlier publication 7,8 where we showed that the permittivity at microwave frequencies and 20 K decreases with Mn. At these low temperatures, the soft mode is the main dielectric contributor as all other relaxation processes are frozen.…”

“…͑a͒ Temperature dependence of tan ␦ at various frequencies, ͑b͒ tan ␦͑T͒ compared with Ј͑T͒, ͑c͒ the frequency dependence of real and imaginary part of the dielectric permittivity, and ͑d͒ the corresponding ColeCole plots for ͑K 1−2x Mn x ᮀ x ͒TaO 3 with x = 0.005. one polar source. 7 The Ј͑T͒ peaks here show signs of superposition of maxima. Here we suggest that there may be up to three distinct sources of relaxational response where two are the off-centering of the Mn ion on the A-side, one from cation vacancy and one is of unknown origin but commonly observed in KTaO 3 samples.…”

“…Furthermore, a description of an increased lattice hardening with increasing Mn substitution and symmetry breaking and formation of nanodomains was discussed. 7,8 To achieve a complete picture of the nanocluster polarization dynamics, a wide range of applied frequencies is necessary where other moderately substituted quantum paraelectric SrTiO 3 and KTaO 3 has been analyzed in such manner. 2,3 So, based on previous investigations of manganese incorporation in single crystal KTaO 3 , 4,5 we assume a substitution mechanism where the manganese is in the form of Mn 2+ and substitutes for K + .…”

Normal and abnormal dielectric relaxation behavior in KTaO3 ceramics

“…Due to this, a plethora of experimental and theoretical investigations have been performed on the low-temperature dielectric properties of KT. [1][2][3][4][5][6][7][8][9][10] Among perovskite materials, the appealing dielectric properties of low dielectric loss and relatively high dielectric permittivity for KT make it attractive for study as a promising microwave material. [11][12][13][14] On the other hand, KT crystal has highly polarizable lattice, which allows strong interaction of impurity-induced dipoles leading to dipole glass state 15 and even to ferroelectric phase transition.…”

Combined Analytical Transmission Electron Microscopy Approach to Reliable Composition Evaluation of KTaO3

“…In general, KTaO 3 in terms of its dielectric properties is known to be very sensitive to the presence of secondary phases, which are formed due to the potassium loss, and point defects related to either A-or B-site dopant, or O vacancies. 13 In the literature, the phase composition of the obtained ceramic is usually determined from the X-ray diffraction (XRD) patterns as well as from the composition-sensitive scanning electron microscope (SEM) images obtained with back-scattered (BE) electrons. By the best of our knowledge, no composition-sensitive microanalysis in either SEM or transmission electron microscope (TEM) that would reveal the exact composition of the material at different synthesis stages has ever been performed.…”